(1) Field of the Invention
The present invention is directed to acoustic devices. In particular, the present invention is directed to diagnostic medical equipment such as stethoscopes.
(2) Description of the Prior Art
Auscultation is the act of listening to the sounds from internal organs of the body. These sounds are used to diagnose abnormalities or disorders in the internal organs for the purpose of prescribing appropriate treatments. The instrument commonly used for auscultation is the acoustic stethoscope, which is one of the most utilized instruments of health care providers. In order to use the stethoscope, an acoustic bell is placed on the body over the organ of interest. The sounds received by the bell are conveyed through a tubular line to ear pieces that are inserted into a physician's ears. Because a stethoscope is a non-invasive means for auscultation, it is an invaluable tool for the medical diagnosis of abnormalities, particularly cardiac, lung and vascular disorders.
The effectiveness of a stethoscope depends on both the ability to conduct body sounds to the ear and the skill and hearing ability of the user. A conventional acoustic stethoscope acts as a low-pass filter. Therefore, the higher frequencies associated with the internal body sounds are filtered out. In addition, a user with poor hearing is less likely to be able to interpret the body sounds delivered through the tubular line. The frequency range for audible sounds is from about 10 Hz to about 15500 Hz; however, most people are not able to hear sounds across the entire audio frequency range. Age and ear disorders cause a decrease in the sensitivity of the ear, in particular to higher frequencies. These limitations can cause a physician to have a distorted or inadequate impression of the sounds originating from the internal organ, which could lead to a misinterpretation of the medical significance of these sounds.
Attempts at overcoming the limitations of conventional acoustic stethoscopes involve amplifying the sounds obtained by the acoustic bell and providing visual indicators of the sounds or functions of internal organs. For example, U.S. Pat. No. 4,672,975 is directed to a stethoscope that includes an electronic device that produces an image of an expanding and contracting heart. The image of the expanding and contracting heart either does not represent actual heart activity of a patient and instead only serves the purpose of entertaining the patient or is formed in correspondence with the heart beats of a patient. The contracting and expanding heart is represented by light emitting diodes or a liquid crystal display, and the image is not limited to a heart-shaped image. The disclosed stethoscope, however, requires a multitude of electronic components including batteries, microphones and other circuitry. All of these components add size, weight, cost and complexity to the stethoscope. Also, the visual image is directed specifically and solely to an indication of patient heart rate.
U.S. Pat. No. 4,783,813 is directed to an electronic sound amplifying stethoscope with visual heart beat and blood flow indicator. The amplification circuitry includes a battery, a microphone and a speaker. A light emitting diode (LED) light source is inserted in series with the amplifier circuit, a switch and the battery. The current flow to the amplifier circuit also energizes the LED such that the intensity of the LED is directly proportional to the volume of sound amplified. The current flow through the LED is responsive to the current fluctuations or power surges in the amplifier and speaker. This stethoscope contains electronic circuitry that requires a power source and adds to the complexity, weight and cost of the stethoscope. Also, although the intensity of the LED changes, it is not clear how this intensity indicates a particular type of body function or any particular qualities of a body function. The LED intensity only indicates the intensity of the audio signal that is being amplified.
U.S. Pat. No. 5,638,453 is directed to a transducer enhanced stethoscope that measures skin temperature and heart rate in addition to amplifying the sound that is transmitted through the stethoscope. The stethoscope includes a pickup head having a top face that includes a pair of semi-circular temperature sensors capable of measuring skin temperature and displaying it on a top readout screen. The bottom face of the pickup head has a semi-circular pulse sensor that uses a transducer to determine the pulse of the body, displaying this information on a bottom readout screen. A battery is housed within the pickup head. This stethoscope requires rather complex electronics and a power source such as a battery that add to the size and cost of the stethoscope. In addition, the electronics are selected to measure and display two specific body measurements, temperature and pulse rate. No visual indication of the heart rate or any other body sound is provided.
U.S. Pat. No. 5,737,429 is directed to a portable, viewable and audible stethoscope for visually and audibly monitoring vital life signs such as heart beat, lung respiration, artery pulse and intestinal sounds. The stethoscope includes sound absorbing cups in contact with an output device that includes a microphone that converts the sounds coming from the absorbing cups into electrical signals. The output device includes an oscilloscope and an electronic circuit assembly for displaying the electrical signals as graphs on the oscilloscope. In order to create a visual indication of the monitored functions, a completely separate assembly that includes an oscilloscope with a picture screen and the necessary control circuitry is used. The oscilloscope is likely to have a significant power demand and associated cost. Therefore, this solution is complex and has a high associated cost.
U.S. Pat. No. 6,396,931 is directed to an electronic stethoscope with diagnostic capability that provides means for comparing a stethoscope sound and oscilloscope image with a typical sound and identified image that has been prerecorded on a magnetic memory disc. Various heart and lung sounds are prerecorded along with a very short diagnosis of the defect causing the sound. If a technician suspects any disorders, that technician presses an appropriate button and adjusts a sliding switch to the location at which matching sounds are heard and seen from a prerecorded diskette. This system is not simply amplifying the sounds of a stethoscope or providing a visual analogue of the sounds. The system is a complex diagnostic tool that requires prerecorded comparisons that a skilled technician can use to determine if the sounds that are heard correlate to a specific condition.
U.S. Patent Application Publication No. US2001/0030077 is directed to a stethoscope with ECG monitor for monitoring and displaying heart sounds and heart electrical activity. The system uses an electronic stethoscope head combined with a standard stethoscope air tube headset assembly. The stethoscope head includes an electrode assembly that conducts electrical signals to a display module that is mounted on the stethoscope body. The display module includes a housing containing an electrical signal processor, a battery power supply and a view screen. The view screen presentation includes a waveform presentation of the heart electrical signal. Other sensor and diagnostic features can also be included such as a blood hemoglobin oxygen saturation sensor and blood sugar detectors. Again, this device requires various electronic components and a power supply, adding complexity and cost to the stethoscope. In addition, the visual information presented is not simply a visual indication of the audible information detected by the stethoscope but is additional diagnostic information that is provided by separate sensors that are specifically arranged and selected to provide a particular type of information.
U.S. Patent Application Publication No. US2002/0071570 is directed to a hybrid stethoscope that enables a physician to hear sounds emanating from an internal region and to concurrently see an analogue waveform of these sounds. The hybrid stethoscope includes a self-sufficient battery-powered visual display module attached to the rear end of the acoustic bell. The display module is provided with a liquid crystal display (LCD) or similar device to exhibit an analog waveform of the audible sounds impinging on the diaphragm of the bell and conveyed to the ears of the physician. This is an electronic system that requires power, a microphone, a liquid crystal display, integrated circuits and other electronic components. The output is a waveform that needs to be related to the body system being monitored and the sounds impinging on the bell.
Therefore, the need exists for a stethoscope that is capable of monitoring sounds produced by internal organs and of simultaneously delivering an audible output of these sounds and a corresponding visual indication. The combined audible and visual output can be used for any type of internal organ and does not require complex or expensive electrical components that have a significant power demand.